boltnut

Hey all. I spend all my time in the C3 section but I'm trying to help my uncle who owns an 84 C4. He will be driving down the road and the engine will cut out. After he pulls over to the side of the road and let's it sit awhile it will start up again. And likely keep doing it for the rest of the afternoon. He can never get very far before it stops again.

It then may be several days before it happens again. He is very frustrated and not getting help from his local corvette mechanic. I was hoping I could get him some new things to try.

He is not computer literate so I will try to answer any questions you have for him. Thanks for any input at all.....

boltnut

Yes it has the crossfire injection.

Lemme

Maybe do a test with the car idling. Monitor as many engine variables as possible (watch all the gauges) and see if it cuts out. May be temperature related, electrical short circuit, fuel issue etc. If possible do a datalog and have a look at what is happening to all the ecm sensor signals.

I also have an 84.

joe paco

your mechaninic should do the basic stuff we all do: verify fuel rail pressure, spark. the MAF sensor should set a code, also need other clues, rich exhaust, etc. mechanic has to check for codes.

you could swap out a dozen parts and not find the one root cause. but, sounds like the ICM, ign conr module, is likely. can be removed and checked at auto zone wherever, replaced for $20. fuel pump should not be intermittent, but fuel filter can be.

lumij3

See what happens with the Voltemeter, if it fluctuates then it is elestrical and he might be losing juice somewhere in the sys. Just my 2 cents, out of my own experience.

pcolt94

This problem just screams at me, bad fuel pump or ignition control module. This should not be too tough just to localize the problem. I would hang a fuel pressure gauge on it and drive it. If it quits and the pressure stays up there, then it's got to be spark related.

A clogged fuel filter would show up all the time with high fuel flow demand with high speed driving or acceleration.

Testing for no spark in the middle of the road is much more difficult than to just look at a pressure gauge (especially if your alone).

navy_vette

My brain is pointing towards ICM. It may be a heat related issue with that as well.

mfi

Its what killed mine..very easy to fix..probably find the heat sink loaded with crud..which kills it..

pcolt94

There is no ICM on an 84. The engines that use the opti's use the ICMs.

But what I think that is trying to be said is the "electronic spark control module". I believe this is the unit that get all the attention from what I know. Distributor module & pick up coil are usually second on the list for the ignition problems.

But I think the "electronic spark control module" is the one that is more heat sensitive.

*As I have called it the wrong description at first also.

joe paco

I may be the only one confused. The Dist module is the only "module" referencd in fsm, 6d4-10, also called ign module in the fsm. ***five pins one end and other goes to pu coil. two leads.

"elec spr ctrl mod" is a new term to me. I am aware of the elec spark control circuit, knock sensor, but no module separate from dist module, which does control spark timing to some degree.

the heat sink grease that GM refers to several times is silicone clear lubricant, their terms. I have had a tube of the clear "grease" for 30 years. it is not the same stuff that is packaged with the "control module" sold by autozone.

what have I overrlooked? and didn't all HEI's have a dist module -by any name, the same function?

joe

pcolt94

Not exactly sure how to answer your question. There is also lots of information if you do a search on "electronic spark control". However, will this picture help.

joe paco

[QUOTE=pcolt94;1578719173]Not exactly sure how to answer your question. There is also lots of information if you do a search on "electronic spark control". However, will this picture help.


pcolt94,
I was unaware that the 84 had a separate "escm," apparently not the same as TPI, ECM. My experience is with 91 L98. I also knew how the ESC on the l98 interfaces with ecm if knock is sensed.

thanks.

sknight88

I had the same thing,bought the car knowing about it. Owner was 4k into chasing the problem down. I did 2 things, bought a new key and under the battery is a series of junctions for the grounds. They were all rusty from a leaky past battery. I cleaned them all up. 3 years later has never stalled out again!

Cliff Harris

I think people refer to the module in the distributor as the ICM - Ignition Control Module.

It's the one labeled DISTRIBUTOR MODULE (AND PICK-UP COIL) in the diagram.

joe paco

yep, dist module, ign module, module are all same thing in the 91 fsm -GM terms. the missing word is "control." I had never heard "electronic spark control module" and had recently rebuilt my 91 dist, never saw it.
actually, ignition is controlled by that module, ESC sensor -knock sensor, and signals from ECM to dist module, from my understanding of it.

gracias, joe

boltnut

Thanks for the help guys. I passed along the info and will report if anything helps. I don't know much about these issues....I'm still playing with carburetors......